It has been reported heretofore that cells containing cathodes made from lithium cobalt oxide (LiCoO.sub.2) or from lithium nickel oxide (LiNiO.sub.2) exhibit favorable electrical and chemical properties which could be of use in the high energy density battery fields.
The three main methods heretofore for the preparation of lithium cobalt oxide (LiCoO.sub.2) are as follows:
1. Molecular proportions of lithium carbonate (Li.sub.2 CO.sub.3) and cobalt carbonate (CoCO.sub.3) are intimately mechanically mixed and pressed into pellets. The pellets are heated in air at 900.degree. C. for 20 hours followed by two further annealings. The quench from high temperature is of utmost importance to preserve the high temperature "rock salt" structure at low temperature.
2. Another similar high temperature solid state reaction is by mixing lithium oxide (Li.sub.2 O.sub.2) and cobalt oxide (CoO) and heating the mixture at 900.degree. C. in air for an extended period (1-3 days).
3. A new variety of lithium cobalt oxide (LiCoO.sub.2) has been obtained by using an extraction exchange reaction of sodium cobalt oxide (NaCoO.sub.2) and lithium chloride (LiCl) in methanol over a three day period.
In all the above three known methods of preparation, either high temperatures or extended times are necessary. The high temperatures and extended times are conditions for grain growth and reduction in surface area. Both these criteria, however, are in opposition to favorable properties for use of the lithium cobalt oxide (LiCoO.sub.2) in a high energy density battery.
The importance of retaining the "rock salt" structure has been emphasized and it is a reflection on the extent of the "work heat" (900.degree. C., 1-2 days) impressed upon the solid mixture to force the solid state reaction to completion.